1. Field of the Invention
The present invention relates to an electric-component mounting system for assembling an electric circuit board, by placing or mounting a plurality of electric components (including electronic components) onto a circuit board.
2. Discussion of Related Art
There is known an electric-component mounting system for mounting a plurality of electric components onto a circuit board such as a printed board. As one type of the electric-component mounting system, there is known a system including a plurality of electric-component mounting units which are arranged in such a manner that permits a plurality of electric components to be successively mounted, by the arranged electric-component mounting units, onto one (hereinafter referred to as a work surface) of opposite surfaces of the circuit board which is held at the other (hereinafter referred to as a supported surface) of the opposite surfaces. In such an electric-component mounting system, the circuit board is moved in a direction in which the electric-component mounting units are arranged, whereby the circuit board is transferred between the arranged electric-component mounting units, so that each of the electric components is mounted onto the work surface of the circuit board by one of the electric-component mounting units which is assigned to mount the electric component. After the electric components have thus mounted onto the circuit board, the electric components are electrically connected to the circuit board by a solder or other suitable means, whereby an electric circuit board as a product is produced.
In such an electric-component mounting system, if each electric-component mounting unit has a relatively wide working area within which the electric components are mountable onto the circuit board by the same unit, it might be possible to mount the electric components at any position on the entire work surface of the circuit board even where the circuit board has a relatively large size. That is, the wide working area of each electric-component mounting unit provides a high degree of freedom in assigning a role to each electric-component mounting unit, thereby making it possible to increase the efficiency of mounting of the electric components onto the circuit board. However, in general, such an electric-component mounting unit having the wide working area has a large size, and accordingly the electric component mounting system is enlarged as a whole, requiring a large floor space for the installation. This would be problematic where the circuit board has a relatively small size, namely, where the wide working area of each electric-component mounting unit is not fully utilized, resulting in a reduction in the production efficiency per unit space of the floor on which the system is installed.
On the other hand, if each electric-component mounting unit has a relatively narrow working area, it would be possible to work with a small-sized circuit board without a reduction in the production efficiency per unit space of the floor. Further, it would be possible to work with also a large-sized circuit board which has a larger area than the narrow working area of each electric-component mounting unit, for example, by dividing the large area of the circuit board into a plurality of sections so that the electric components are subsequently mounted onto the plurality of sections of the large area by the respective electric-component mounting units. However, there would be a case where the large-sized circuit board is partially superposed on the working area of one of electric-component mounting units while the electric components are being mounted onto the large-sized circuit board by the adjacent electric-component mounting unit. In such a case, the electric-component mounting unit in question is obliged to suspend its mounting operation, resulting in a reduction in the operation efficiency of the electric-component mounting system.
It might be considered possible to activate the electric-component mounting unit in question to mount the electric components onto the part of the large-sized circuit board which is superposed on the working area of the same unit, so that the mounting operations of the respective adjacent units are performed concurrently on the large-sized circuit board. This arrangement might be somewhat effective to avoid the reduction in the operation efficiency of the electric-component mounting system. However, where the superposed part is small, the same unit is obliged to suspend its mounting operation for a while after all. Further, between each adjacent pair of the electric-component mounting units, there commonly exists a non-working area over which the electric components are not mountable onto the circuit board by either one of the adjacent units. The existence of such a non-working area makes it extremely difficult for the electric-component mounting units to efficiently share the area of the circuit board or to share the electric components (to be mounted on the area of the circuit board), resulting in a reduction in the operation efficiency of the electric-component mounting system.